Heat exchanger

ABSTRACT

A heat exchanger to be used as a heater core includes a pair of header tanks spaced apart from each other, a plurality of flat heat exchange tubes which are disposed between the two header tanks at predetermined intervals along a longitudinal direction of the header tanks with their width direction coinciding with an air flow direction and whose opposite end portions are connected to the header tanks, and a plurality of corrugate fins each disposed between the adjacent heat exchange tubes. Each heat exchange tube has an inner height Ht of 1.2 mm to 1.7 mm and a width of 18 mm to 24 mm as measured in the air flow direction. Each corrugate fin has a fin height Hf of 4.0 mm to 7.5 mm. This heat exchanger exhibits excellent heat radiation performance and low resistance to air flow and water flow.

BACKGROUND OF THE INVENTION

The present invention relates to a heat exchanger preferably used as,for example, a heater core to be incorporated into a car airconditioner.

Herein and in the appended claims, the term “aluminum” encompassesaluminum alloys in addition to pure aluminum.

A conventionally known heater core for use in a car air conditionerincludes a pair of header tanks spaced apart from each other, aplurality of flat heat exchange tubes which are disposed between the twoheader tanks at predetermined intervals along a longitudinal directionof the header tanks with their width direction coinciding with an airflow direction and whose opposite end portions are connected to thecorresponding header tanks, and a plurality of corrugate fins eachincluding wave crest portions, wave trough portions, and flat connectionportions connecting together the corresponding wave crest portions andwave trough portions, and each disposed between the adjacent heatexchange tubes. In this heater core, the tube height of the heatexchange tube (thickness along the longitudinal direction of a header)is 1.4 mm to 1.8 mm; the thickness of an elongated aluminum sheet usedto form the heat exchange tube, or the tube wall thickness of the heatexchange tube, is 0.4 mm; the inner height of the heat exchange tube(tube height−tube wall thickness×2) is 0.6 mm to 1.0 mm; the width ofthe corrugate fin as measured in the air flow direction is 21 mm to 32mm; and the fin height of the corrugate fin, or the direct distancebetween the wave crest portion and the wave trough portion, is 2.5 mm to5.0 mm (refer to Japanese Patent No. 3459271).

In recent years, heater cores have required further improvement inperformance. The heater core disclosed in the above-mentioned patentexhibits excellent heat radiation performance, but has high resistanceto air flow and water flow. Therefore, the heater core fails to have therequired performance as a whole.

In order to optimize heat radiation amount, resistance to air flow, andresistance to water flow, which are performance factors of a heatercore, the inventors of the present invention focused on the inner heightof each heat exchange tube and the fin height of a corrugate fin andhave achieved the present invention.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above problem and toprovide a heat exchanger which, when used as a heater core, exhibitsexcellent heat radiation performance and has low resistance to air flowand water flow.

To achieve the above object, the present invention comprises thefollowing modes.

1) A heat exchanger comprising:

a pair of header tanks spaced apart from each other;

a plurality of flat heat exchange tubes which are disposed between thetwo header tanks at predetermined intervals along a longitudinaldirection of the header tanks with their width direction coinciding withan air flow direction and whose opposite end portions are connected tothe corresponding header tanks; and

a plurality of corrugate fins each comprising wave crest portions, wavetrough portions, and flat connection portions connecting together thecorresponding wave crest portions and wave trough portions, and eachdisposed between the adjacent heat exchange tubes;

wherein each heat exchange tube has an inner height of 1.2 mm to 1.7 mmand a width of 18 mm to 24 mm as measured in the air flow direction, andeach corrugate fin has a fin height of 4.0 mm to 7.5 mm, the fin heightbeing the direct distance between the wave crest portion and the wavetrough portion.

2) A heat exchanger according to par. 1), wherein the inner height ofeach heat exchange tube is 1.3 mm to 1.5 mm.

3) A heat exchanger according to par. 1), wherein the fin height of eachcorrugate fin is 5.0 mm to 6.5 mm.

4) A heat exchanger according to par. 1), wherein each heat exchangetube comprises a pair of flat walls facing each other, two side wallsextending between opposite side ends of the two flat walls, and areinforcement wall extending between widthwise intermediate portions ofthe two flat walls;

one of the two flat walls comprises a first flat-wall-forming portion;

the other flat wall comprises two second flat-wall-forming portionswhich are formed integrally with the corresponding opposite side ends ofthe first flat-wall-forming portion via the side walls and whose sideends located opposite the corresponding side walls butt against eachother;

the reinforcement wall comprises two reinforcement-wall-forming portionswhich are formed integrally with the corresponding butting side ends ofthe two second flat-wall-forming portions and in such a manner as toproject toward the first flat-wall-forming portion and whose projectingend portions abut the first flat-wall-forming portion; and

two bend portions are formed integrally with corresponding projectingends of the two reinforcement-wall-forming portions and in such a manneras to extend toward the corresponding side walls, and are joined to thefirst flat-wall-forming portion.

5) A heat exchanger according to par. 4), wherein the inner height ofeach heat exchange tube is the direct distance between an inner surfaceof the first flat-wall-forming portion and an inner surface of thesecond flat-wall-forming portion.

The above-mentioned heat exchanger is used as, for example, a heatercore of a car air conditioner.

The heat exchanger of par. 1), when used as a heater core of a car airconditioner, exhibits excellent heat radiation performance andimplements prevention of an increase in resistance to air flow and waterflow.

The heat exchanger of par. 2) or 3) enhances the effect yielded by theheat exchanger of par. 1).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing the overall configuration of a heatercore for a car air conditioner to which a heat exchanger of the presentinvention is applied;

FIG. 2 is an enlarged sectional view taken along line A-A of FIG. 1;

FIG. 3 is a sectional view taken along line B-B of FIG. 2;

FIG. 4 is a graph of the inner height Ht of a heat exchange tube vs. theratio Q/DPa between heat radiation amount and resistance to air flow andthe ratio Q/DPw between heat radiation amount and resistance to waterflow; and

FIG. 5 is a graph of the fin height Hf vs. the ratio Q/DPa between heatradiation amount and resistance to air flow and the ratio Q/DPw betweenheat radiation amount and resistance to water flow.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will next be described in detailwith reference to the drawings. The present embodiment is an applicationof a heat exchanger of the present invention to a heater core of a carair conditioner.

The upper, lower, left-hand, and right-hand sides of FIG. 1 will bereferred to as “upper,” “lower,” “left,” and “right,” respectively. Thefar side of the paper on which FIG. 1 appears (the upper side of FIG. 2)is referred to as the “front,” and the opposite side as the “rear.

FIG. 1 shows the general configuration of a heater core for a car airconditioner to which a heat exchanger of the present invention isapplied. FIGS. 2 and 3 show the configuration of essential portions ofthe heater core.

In FIG. 1, a heater core 1 includes an upper header tank 2 and a lowerheader tank 3 which are made of aluminum, are vertically spaced apartfrom each other, and are elongated in the left-right direction, and aheat exchange core section 4 provided between the upper and lower headertanks 2 and 3.

Left end portions of the upper and lower header tanks 2 and 3 projectleftward beyond the heat exchange core section 4. An outlet pipe 5 isconnected to a leftward-projecting portion of the upper header tank 2,and an inlet pipe 6 is connected to a leftward-projecting portion of thelower header tank 3.

The heat exchange core section 4 includes a plurality of flat heatexchange tubes 7 made of aluminum which are disposed at predeterminedintervals along the left-right direction with their width directioncoinciding with the front-rear direction (air flow direction) and whoseupper and lower end portions are connected to the upper and lower headertanks 2 and 3, respectively; a plurality of corrugate fins 8 made ofaluminum which are each disposed between the adjacent heat exchangetubes 7 and outside the leftmost and rightmost heat exchange tubes 7 andare brazed to the heat exchange tubes 7; and two side plates 9 disposedoutside and brazed to the corresponding leftmost and rightmost corrugatefins 8. The upper and lower end portions of the heat exchange tubes 7are brazed to the upper and lower header tanks 2 and 3, respectively,while being inserted into corresponding tube insertion holes (not shown)formed in the upper and lower header tanks 2 and 3.

As shown in FIGS. 2 and 3, each heat exchange tube 7 is formed bytubularly bending an elongated aluminum brazing sheet having a brazingmaterial layer on at least one side thereof, in such a manner that thebrazing material comes outside. The heat exchange tube 7 includes leftand right walls 11 and 12 facing each other (a pair of flat walls);front and rear side walls 13 and 14 extending between the front sideends and between the rear side ends, respectively, of the left and rightwalls 11 and 12; and a reinforcement wall 15 extending between centralportions with respect to a width direction of the left and right walls11 and 12. The right wall 12 is formed of a single right-wall-formingportion 12A. The left wall 11 is formed of two left-wall-formingportions 11A and 11B. The left-wall-forming portions 11A and 11B areintegral with the front and rear side ends, respectively, of theright-wall-forming portion 12A via the front and rear side walls 13 and14, respectively. Side ends, located on a side opposite the side walls13 and 14, of the left-wall-forming portions 11A and 11B butt againsteach other. The reinforcement wall 15 is formed of tworeinforcement-wall-forming portions 15A which are formed integrally withthe corresponding butting side ends of the left-wall-forming portions11A and 11B and in such a manner as to project rightward and whoseprojecting end portions abut and are brazed to the right-wall-formingportion 12A. Two bend portions 15B are formed integrally withcorresponding projecting ends (right ends) of the tworeinforcement-wall-forming portions 15A and in such a manner as toextend toward the corresponding side walls 13 and 14, and are brazed tothe right-wall-forming portion 12A.

The width Wt of the heat exchange tube 7 as measured in the front-reardirection is 18 mm to 24 mm. The inner height Ht of the heat exchangetube 7; i.e., the direct distance between the inner surfaces of the leftand right walls 11 and 12 as measured in a region where the bendportions 15B are absent, is 1.2 mm to 1.7 mm. Preferably, the innerheight Ht of the heat exchange tube 7 is 1.3 mm to 1.5 mm. The wallthickness of the heat exchange tube 7 is 0.1 mm to 0.4 mm; for example,0.2 mm. The wall thickness of the heat exchange tube 7 is determined inconsideration of manufacture constraints and strength requirements.

The corrugate fin 8 is formed in a corrugated form from an aluminumbrazing sheet having a brazing material layer on each of opposite sidesthereof. The corrugate fin 8 includes wave crest portions 8 a, wavetrough portions 8 b, and flat horizontal connection portions 8 c eachconnecting together the wave crest portion 8 a and the wave troughportion 8 b. A plurality of louvers 16 are formed at the connectionportions 8 c in such a manner as to be juxtaposed in the front-reardirection. The width of the corrugate fin 8 as measured in thefront-rear direction is equal to the width of the heat exchange tube 7as measured in the front-rear direction. The wave crest portions 8 a andthe wave trough portions 8 b of the corrugate fins 8 are brazed to theheat exchange tubes 7 and the side plates 9.

The fin height Hf of the corrugate fin 8; i.e., the direct distancebetween the wave crest portion 8 a and the wave trough portion 8 b, is4.0 mm to 7.5 mm, preferably 5.0 mm to 6.5 mm. When P represents thepitch of the adjacent wave crest portions 8 a of the corrugate fin 8,the fin pitch Pf is equal to P/2; specifically, 0.8 mm to 3.0 mm,preferably 1.5 mm. The wall thickness of the corrugate fin 8 is 0.02 mmto 0.1 mm; for example, 0.06 mm. The fin pitch Pf and wall thickness ofthe corrugate fin 8 are determined in consideration of manufactureconstraints, strength requirements, and resistance to air flow.

The inner height Ht of the heat exchange tube 7 is set to 1.2 mm to 1.7mm from the results of computer simulation shown in FIG. 4. Thiscomputer simulation was performed under the following conditions whilethe inner height Ht of the heat exchange tube 7 was varied: the heightof the heat exchange core section 4 is 140 mm; the width of the heatexchange core section 4 as measured in the left-right direction is 145mm; the width Wt of the heat exchange tube 7 as measured in thefront-rear direction is 21 mm; the wall thickness of the heat exchangetube 7 is 0.2 mm; the fin height Hf of the corrugate fin 8, or thedirect distance between the wave crest portion 8 a and the wave troughportion 8 b, is 5.7 mm; the fin pitch Pf of the corrugate fin 8, or thepitch of the connection portions 8 c, is 1.5 mm; and the wall thicknessof the corrugate fin 8 is 0.06 mm.

The vertical axis of the graph shown in FIG. 4 represents the ratioQ/DPa between heat radiation amount and resistance to air flow and theratio Q/DPw between heat radiation amount and resistance to water flow.In order to improve the performance of the heater core 1, both of theratios Q/DPa and Q/DPw must be increased. In order to increase Q/DPathrough reduction in resistance to air flow, the fin height Hf must beincreased through reduction in the inner height Ht of the heat exchangetube 7. However, in this case, resistance to water flow increases. Inorder to increase Q/DPw through reduction in resistance to water flow,the inner height Ht of the heat exchange tube 7 must be increasedthrough reduction in the fin height Hf. However, in this case,resistance to air flow increases. From the simulation resultsrepresented by the graph of FIG. 4, the inner height Ht of the heatexchange tube 7 is set to a range of 1.2 mm to 1.7 mm in which both ofQ/DPa and Q/DPw assume respectively preferable values. As is apparentfrom FIG. 4, the inner height Ht of the heat exchange tube 7 ispreferably 1.3 mm to 1.5 mm. The lower limit of the inner height Ht ofthe heat exchange tube 7 is set to 0.7 mm, since the heat exchange tube7 having an inner height Ht of less than 0.7 mm is difficult tomanufacture.

The fin height Hf of the corrugate fin 8 is set to 4.0 mm to 7.5 mm fromthe results of computer simulation shown in FIG. 5. This computersimulation was performed under the following conditions while the finheight Hf of the corrugate fin 8 was varied: the height of the heatexchange core section 4 is 140 mm; the width of the heat exchange coresection 4 as measured in the left-right direction is 145 mm; the widthWt of the heat exchange tube 7 as measured in the front-rear directionis 21 mm; the inner height Ht of the heat exchange tube 7 is 1.4 mm; thewall thickness of the heat exchange tube 7 is 0.2 mm; the fin pitch Pfof the corrugate fin 8, or the pitch of the connection portions 8 c, is1.5 mm; and the wall thickness of the corrugate fin 8 is 0.06 mm.

The vertical axis of the graph shown in FIG. 5 represents the ratioQ/DPa between heat radiation amount and resistance to air flow and theratio Q/DPw between heat radiation amount and resistance to water flow.In order to improve the performance of the heater core 1, both of theratios Q/DPa and Q/DPw must be increased. In order to increase Q/DPathrough reduction in resistance to air flow, the fin height Hf must beincreased through reduction in the inner height Ht of the heat exchangetube 7. However, in this case, resistance to water flow increases. Inorder to increase Q/DPw through reduction in resistance to water flow,the inner height Ht of the heat exchange tube 7 must be increasedthrough reduction in the fin height Hf. However, in this case,resistance to air flow increases. From the simulation resultsrepresented by the graph of FIG. 5, the fin height Hf of the corrugatefin 8 is set to a range of 4.0 mm to 7.5 mm in which both of Q/DPa andQ/DPw assume respectively preferable values. As is apparent from FIG. 5,the fin height Hf of the corrugate fin 8 is preferably 5.0 mm to 6.5 mm.

In the above-described heater core 1, high-temperature engine-coolingwater is transferred from an engine into the lower header tank 3 throughthe inlet pipe 6. The high-temperature engine-cooling water which hasflowed into the lower header tank 3 dividedly flows into the heatexchange tubes 7, flows upward through the heat exchange tubes 7, andthen enters the upper header tank 2. The high-temperature engine-coolingwater which has flowed into the upper header tank 2 flows out throughthe outlet pipe 5 and then returns to the engine. Notably, thehigh-temperature engine-cooling water may be transferred from the engineto the heater core 1 and an radiator or may be transferred from theengine to the radiator only.

1. A heat exchanger comprising: a pair of header tanks spaced apart fromeach other; a plurality of flat heat exchange tubes which are disposedbetween the two header tanks at predetermined intervals along alongitudinal direction of the header tanks with their width directioncoinciding with an air flow direction and whose opposite end portionsare connected to the corresponding header tanks; and a plurality ofcorrugate fins each comprising wave crest portions, wave troughportions, and flat connection portions connecting together thecorresponding wave crest portions and wave trough portions, and eachdisposed between the adjacent heat exchange tubes; wherein each heatexchange tube has an inner height of 1.2 mm to 1.7 mm and a width of 18mm to 24 mm as measured in the air flow direction, and each corrugatefin has a fin height of 4.0 mm to 7.5 mm, the fin height being thedirect distance between the wave crest portion and the wave troughportion.
 2. A heat exchanger according to claim 1, wherein the innerheight of each heat exchange tube is 1.3 mm to 1.5 mm.
 3. A heatexchanger according to claim 1, wherein the fin height of each corrugatefin is 5.0 mm to 6.5 mm.
 4. A heat exchanger according to claim 1,wherein each heat exchange tube comprises a pair of flat walls facingeach other, two side walls extending between opposite side ends of thetwo flat walls, and a reinforcement wall extending between widthwiseintermediate portions of the two flat walls; one of the two flat wallscomprises a first flat-wall-forming portion; the other flat wallcomprises two second flat-wall-forming portions which are formedintegrally with the corresponding opposite side ends of the firstflat-wall-forming portion via the side walls and whose side ends locatedopposite the corresponding side walls butt against each other; thereinforcement wall comprises two reinforcement-wall-forming portionswhich are formed integrally with the corresponding butting side ends ofthe two second flat-wall-forming portions and in such a manner as toproject toward the first flat-wall-forming portion and whose projectingend portions abut the first flat-wall-forming portion; and two bendportions are formed integrally with corresponding projecting ends of thetwo reinforcement-wall-forming portions and in such a manner as toextend toward the corresponding side walls, and are joined to the firstflat-wall-forming portion.
 5. A heat exchanger according to claim 4,wherein the inner height of each heat exchange tube is the directdistance between an inner surface of the first flat-wall-forming portionand an inner surface of the second flat-wall-forming portion.